In January 1968 I arrived in Mendi, in what was then the Territory of Papua and New Guinea. I was to be a teacher at a high school that didn't yet exist.

The site was the old Methodist mission a mile from town. There was a weatherboard house which I would share with three other new teachers, and a line of dormitories made of bush materials, now decaying. What we didn't have were classrooms. Half of the 'kids' we met on our first official morning had been waiting up to seven years for the high school to open. They were adults – my age, or older. And for the first eight weeks they, not us, were the teachers. We 'newchums' learned to rope-pull whole trees, weave pitpit mat, and pull and tie kunai. The bond that grew wasn't teacher-pupil, it was friendship and mutual respect.

Being a boarding school, we had students from every part of the southern highlands andelsewhere in the country. Our Mendi students also boarded, but often visited their home villages on weekends. There was little for us teachers to do on weekends except read, prepare lessons or drink, so we turned amateur anthropologists, asking the Mendi students to inform us of any events happening back home. And they obliged, giving us advance notice of weddings and funerals, pig kills, gift exchanges and 'singsings'. On a Friday straight after school, or dawn on Saturday, we'd be off with a rucksack, a sleeping bag, and a very willing student as guide and interpreter. Arriving as the teachers of their sons or daughters, we were welcomed, fed, slept. It didn't take long to realise that we were both fascinated spectators at massive gatherings to which we were irrelevant, and witnesses to a cultural web that was unravelling.

I first heard of the 'timp' when I went home with Robert Temo into the Lai Valley. His father was a Big Man. Robert was afraid of him. I could see why when I met him, but he was preoccupied. A man was sick, they had to divine the reason. I asked if I could be present. Temo was clearly not a man intimidated by white skin, but I was a guest. He grudgingly said yes to these two noninitiates, one his own son. I chewed ginger root to cleanse me, spat it onto a woven and painted cane wand, and was admitted to the 'timp' house. The sick man lay before an altar. While Temo chanted, a pig was clubbed and held so that the blood pouring from the snout anointed a nest of ochred stones. Later, Robert admitted that he had understood little more of the chanting than I had, the divination ritual having been conducted in a 'hide' language taught to his father by the timp's previous owner.

I asked about 'timp' whenever I found a man willing to talk. It was a set of ancestor-propitiation rituals 'bought' from groups to the south of Mendi. After six or seven years the power in the rituals waned. Then a new set was bought and the cycle began again.

In 1969 at Bela I was present at the dissolution ceremonies for their last 'timp' cycle. The old men stated sadly that it was the last. None of the young men knew about or were interested in such things any more. The 'corpse' of the 'timp' – its ritual paraphernalia, the saved jaws of slaughtered pigs, the ochred stones – was bundled up and lashed to a pole. I sat up much of the night with the men keeping vigil over the corpse. Before dawn the 'timp' house was destroyed. The conical 'timpsonk' masks were donned for the last time and the men wearing them dashed around the dance ground clearing it of unwelcome spirits and terrifying those children who'd never seen the masks before. The corpse was then paraded at the head of the dancers before being whisked away to be secretly buried. I was conscious as I stood there holding my camera of being both a witness to and a reason for the 'timp's' demise.

Then in 1998 a former student, Wonomi Huka, contacted me through a friend to ask if I still had the photographs I took that day. Young people were asking about the 'timp'! Thrilled, I sent him copies of all I had, some of which you see here.